Cmos image sensor and method of operating the same

ABSTRACT

A CMOS image sensor includes a pixel array unit, a row selection unit, and a logic circuit. The pixel array unit is used for sensing an object. The pixel array unit includes M pixels and P multiplexers wherein each of the M pixels is electrically connected to one of the P multiplexers. The row selection unit and the logic circuit are electrically connected to the P multiplexers. The row selection unit is used for generating a row selection signal. The logic circuit is used for determining a sensing region corresponding to the object wherein the sensing region includes N of the M pixels. Furthermore, the logic circuit controls Q multiplexers, which are electrically connected to the N pixels, to transmit the row selection signal to the N pixels.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a complementary metal oxide semiconductor(CMOS) image sensor and a method of operating the same and, moreparticularly, to a CMOS image sensor and a method of operating the samecapable of improving fabrication yield rate through self-calibration.

2. Description of the Prior Art

Since image sensors have been developed well and image processing speedhas been improved, people have paid much attention to optical touchscreen. So far the image sensor is divided into a charge coupled device(CCD) image sensor and CMOS image sensor. In general, the CCD imagesensor has less noise and better image quality than the CMOS sensor.However, signal processing circuits of the CMOS image sensor can beintegrated into single chip so as to minimize electronic device.Furthermore, the CMOS image sensor has lower power consumption than theCCD image sensor, so it has become more and more popularly.

Referring to FIG. 1, FIG. 1 is a schematic diagram illustrating anoptical touch screen 1 of the prior art. As shown in FIG. 1, the opticaltouch screen 1 comprises a touch panel 10 and two CMOS image sensors 12and 14. The CMOS image sensors 12 and 14 are respectively disposed atboth sides of the touch panel 10. When a user uses an object 16, such asfinger, stylus, or the like, to operate the touch panel 10, the CMOSimage sensors 12 and 14 will sense a projection of the object 16.Afterward, if an angle between the projection and the touch position isknown and a distance between the two CMOS image sensors 12 and 14 can beobtained, a coordinate of the touch position can be then calculated.

Referring to FIGS. 2 and 3, FIG. 2 is a schematic diagram illustrating amoving trajectory 160 of the object 16 projected on the CMOS imagesensor 12 shown in FIG. 1, and FIG. 3 is a schematic diagramillustrating a moving trajectory 160′ of the object 16 projected on theCMOS image sensor 12 shown in FIG. 1. For example, if the CMOS imagesensor 12 is attached to the touch panel 10 without deviation orobliqueness, the moving trajectory 160 of the object 16, which isprojected on a pixel array unit 120 of the CMOS image sensor 12, has arectangular shape, as shown in FIG. 2. However, if the CMOS image sensor12 is attached to the touch panel 10 with deviation or obliqueness dueto assembly tolerance, the moving trajectory 160′ of the object 16,which is projected on the pixel array unit 120 of the CMOS image sensor12, has an oblique shape, as shown in FIG. 3. If the moving trajectory160′ of the object 16 is oblique, the read-out circuit 122 needs to readmore pixel data for following algorithm so as to eliminate the influenceof assembly tolerance. Consequently, operating frequency and powerconsumption of the system will increase a lot.

SUMMARY OF THE INVENTION

An objective of the invention is to provide a CMOS image sensor and amethod of operating the same capable of improving fabrication yield ratethrough self-calibration so as to solve the aforesaid problems.

According to an embodiment of the invention, the CMOS image sensorcomprises a pixel array unit, a row selection unit and a logic circuit.The pixel array unit is used for sensing an object. The pixel array unitcomprises M pixels and P multiplexers. Each of the M pixels iselectrically connected to one of the P multiplexers wherein M is apositive integer and P is a positive integer smaller than or equal to M.The row selection unit and the logic circuit are electrically connectedto the P multiplexers. The row selection unit is used for generating arow selection signal. The logic circuit is used for determining asensing region corresponding to the object. The sensing region comprisesN of the M pixels and N is a positive integer smaller than or equal toM. The logic circuit further controls Q multiplexers, which areelectrically connected to the N pixels, to transmit the row selectionsignal to the N pixels wherein Q is a positive integer smaller than orequal to N and smaller than or equal to P.

According to another embodiment of the invention, the method ofoperating the CMOS image sensor comprises steps of: sensing an object bya pixel array unit wherein the pixel array unit comprises M pixels and Pmultiplexers, each of the M pixels is electrically connected to one ofthe P multiplexers, M is a positive integer, and P is a positive integersmaller than or equal to M; determining a sensing region correspondingto the object wherein the sensing region comprises N of the M pixels andN is a positive integer smaller than or equal to M; generating a rowselection signal; and controlling Q multiplexers, which are electricallyconnected to the N pixels, to transmit the row selection signal to the Npixels wherein Q is a positive integer smaller than or equal to N andsmaller than or equal to P.

According to another embodiment of the invention, the CMOS image sensorcomprises a pixel array unit, a row selection unit, a read-out circuitand a logic circuit. The read-out circuit and the row selection unit areelectrically connected to the pixel array unit. The logic circuit iselectrically connected to the read-out circuit. The pixel array unit isused for sensing an object and comprises M pixels, wherein M is apositive integer. The row selection unit is used for generating a rowselection signal wherein the row selection signal controls the M pixelsto output signals. The read-out circuit is used for reading signalsgenerated by the M pixels. The logic circuit is used for determining asensing region corresponding to the object wherein the sensing regioncomprises N of the M pixels and N is a positive integer smaller than orequal to M. Afterward, the logic circuit determines a first pixel and alast pixel for each row within the sensing region and controls theread-out circuit to read the first pixel through the last pixel of eachrow in row-major order, so as to output signals generated by the Npixels.

According to another embodiment of the invention, the method ofoperating the CMOS image sensor comprises steps of: sensing an object bya pixel array unit wherein the pixel array unit comprises M pixels and Mis a positive integer; determining a sensing region corresponding to theobject wherein the sensing region comprises N of the M pixels and N is apositive integer smaller than or equal to M; generating a row selectionsignal for controlling the M pixels to output signals; determining afirst pixel and a last pixel for each row within the sensing region;reading the first pixel through the last pixel of each row in row-majororder; and outputting signals generated by the N pixels.

Therefore, according to the CMOS image sensor and the method ofoperating the same mentioned in the above, the invention only needs tooutput pixel data within the sensing region to eliminate the influenceof assembly tolerance, so as to reduce operating frequency and powerconsumption substantially.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating an optical touch screen ofthe prior art.

FIG. 2 is a schematic diagram illustrating a moving trajectory of theobject projected on the CMOS image sensor shown in FIG. 1.

FIG. 3 is a schematic diagram illustrating a moving trajectory of theobject projected on the CMOS image sensor shown in FIG. 1.

FIG. 4 is a schematic diagram illustrating a CMOS image sensor accordingto an embodiment of the invention.

FIG. 5 is a schematic diagram illustrating the pixel array unit shown inFIG. 4 having a 3*3 pixel array.

FIG. 6 is a schematic diagram illustrating a circuit of the CMOS imagesensor shown in FIG. 5.

FIG. 7 is a schematic diagram illustrating the sensing region shown inFIG. 5 with a dummy pixel.

FIG. 8 is a flowchart illustrating a method of operating the CMOS imagesensor according to the invention.

FIG. 9 is a flowchart illustrating a method of operating the CMOS imagesensor according to another embodiment of the invention.

FIG. 10 is a schematic diagram illustrating a circuit of a CMOS imagesensor according to another embodiment of the invention.

FIG. 11 is a schematic diagram illustrating a CMOS image sensoraccording to another embodiment of the invention.

FIG. 12 is a time sequence diagram illustrating reading order of pixeldata.

FIG. 13 is a schematic diagram illustrating a CMOS image sensoraccording to another embodiment of the invention.

FIG. 14 is a schematic diagram illustrating the pixel array unit shownin FIG. 13 having a 3*3 pixel array.

FIG. 15 is a schematic diagram illustrating a circuit of the CMOS imagesensor shown in FIG. 14.

FIG. 16 is a schematic diagram illustrating the sensing region shown inFIG. 14 with a dummy pixel.

FIG. 17 is a schematic diagram illustrating a sensing region accordingto another embodiment of the invention.

FIG. 18 is a flowchart illustrating a method of operating the CMOS imagesensor according to another embodiment of the invention.

FIG. 19 is a flowchart illustrating a method of operating the CMOS imagesensor according to another embodiment of the invention.

DETAILED DESCRIPTION

Referring to FIG. 4, FIG. 4 is a schematic diagram illustrating a CMOSimage sensor 3 according to an embodiment of the invention. As shown inFIG. 4, the CMOS image sensor 3 comprises a pixel array unit 30, a rowselection unit 32, a logic circuit 34 and a read-out circuit 36. The rowselection unit 32, the logic circuit 34 and the read-out circuit 36 areelectrically connected to the pixel array unit 30.

The pixel array unit 30 is used for sensing an object (not shown) or amoving trajectory thereof. In this embodiment, the pixel array unit 30comprises M pixels 300 and P multiplexers 320 wherein each of the Mpixels 300 is electrically connected to one of the P multiplexers 302, Mis a positive integer, and P is a positive integer smaller than or equalto M. For further description, if P is equal to M, an amount of thepixels 300 is the same as that of the multiplexers 302 and eachmultiplexer 302 is electrically connected to a unique pixel 300. On theother hand, if P is smaller than M, an amount of the multiplexers 302 isless than that of the pixels 300 and each multiplexer 302 iselectrically connected to at least one pixel 300. The pixel array unit30 shown in FIG. 4 comprises the same amount of pixels 300 andmultiplexers 302 for illustrative purpose. For example, if the pixelarray unit 30 has a 640*480 pixel array and an amount of the pixels 300is the same as that of multiplexers 302, both M and P are equal to640*480. In other words, the pixel array unit 30 comprises 640*480pixels 300 and 640*480 multiplexers 302. In addition, the pixel 300 canabsorb light reflected from an object and then transform the absorbedlight into an electric signal. The pixel 300 usually consists oftransistors and photo diodes. It should be noted that the structure andprinciple of the pixel 300 can be easily achieved by one skilled in theart and thus will not be described in detail here.

The row selection unit 32 receives a time sequence signal and a controlsignal from a controller (not shown) and then generates a row selectionsignal. The row selection signal is used for controlling the pixels 300of the pixel array unit 30 to output data. The logic circuit 34 is usedfor determining a sensing region corresponding to an object or a movingtrajectory sensed by the pixel array unit 30. The sensing regioncomprises N of the M pixels 300 wherein N is a positive integer smallerthan or equal to M. Afterward, the logic circuit 34 controls Qmultiplexers 302, which are electrically connected to the N pixels 300,to transmit the row selection signal to the N pixels 300 wherein Q is apositive integer smaller than or equal to N and smaller than or equal toP. For example, in the pixel array unit 30 shown in FIG. 4, Q is equalto N and smaller than P. The read-out circuit 36 is used for readingsignals generated by the N pixels 300 of the sensing region.

Referring to FIG. 5, FIG. 5 is a schematic diagram illustrating thepixel array unit 30 shown in FIG. 4 having a 3*3 pixel array. The 3*3pixel array shown in FIG. 5 is used, for example, to depict features ofthe invention. In this embodiment, the pixel array unit 30 comprises thesame amount of pixels 300 and multiplexers 302. That is to say, theaforesaid M and P both are equal to 9. Also, referring to FIG. 6, FIG. 6is a schematic diagram illustrating a circuit of the CMOS image sensor 3shown in FIG. 5.

When a user uses an object (not shown), such as finger, stylus or thelike, to operate an optical positioning system (not shown) equipped withthe CMOS image sensor 3, the pixel array unit 30 will sense the objector a moving trajectory thereof. Afterward, the logic circuit 34determining a sensing region 304 according to the object or the movingtrajectory thereof sensed by the pixel array unit 30. As shown in FIG.5, the sensing region 304 comprises five pixels P1, P2, P5, P6 and P9.That is to say, the aforesaid N and Q both are equal to 5. Then, thelogic circuit 34 controls the multiplexers 302, which are electricallyconnected to the aforesaid five pixels, to transmit the row selectionsignal to the five pixels and enables the read-out circuit 36 to readsignals generated by the five pixels within the sensing region 304 inrow-major order. In other words, the red-out circuit 36 will read thepixels P2, P6, P1, P5 and P9 within the sensing region 304 in order.That is to say, the first row read by the read-out circuit 36 includesthe pixels P2 and P6 and the second row read by the read-out circuit 36includes the pixels P1, P5 and P9. In this embodiment, the sensingregion 304 is variable and can be set through self-calibration whilebooting. Furthermore, when the object or the moving trajectory thereofhas a random shape, the logic circuit 34 may determine the sensingregion as a parallelogram including the object or the moving trajectorythereof so as to prevent the following algorithm from gettingcomplicated.

It should be noted that because the sensing region 304 shown in FIG. 5exceeds a real region of the pixel array unit 30, the scanning time maybecome unstable every time and thus the calculation of exposure time mayincrease. To solve this problem, the read-out circuit 36 of theinvention can add dummy pixel (s) to the sensing region 304 whilereading pixel data so as to keep the scanning time in constant everytime and simplify the calculation of exposure time. Referring to FIG. 7,FIG. 7 is a schematic diagram illustrating the sensing region 304 shownin FIG. 5 with a dummy pixel P0. As shown in FIG. 7, after adding thedummy pixel P0, the pixels within the sensing region 304 are arranged asa parallelogram and an amount of pixels in each row is the same.Accordingly, the scanning time can be kept in constant every time.

Referring to FIG. 8, FIG. 8 is a flowchart illustrating a method ofoperating the CMOS image sensor according to the invention. Also,referring to FIGS. 4 to 6 along with the aforesaid CMOS image sensor 3,the method of operating the CMOS image sensor of the invention comprisesthe following steps.

In the beginning, step S100 is performed to sense an object or a movingtrajectory thereof by the pixel array unit 30. Afterward, step S102 isperformed to determine the sensing region 304 corresponding to theobject or the moving trajectory thereof. Step S104 is then performed togenerate a row selection signal. Step S106 is then performed to controlthe multiplexers, which are electrically connected to the pixels P2, P6,P1, P5 and P9 within the sensing region 304, to transmit the rowselection signal to the pixels P2, P6, P1, P5 and P9. Finally, step S108is performed to read signals generated by the pixels P2, P6, P1, P5 andP9 of the sensing region 304 in row-major order.

Referring to FIG. 9, FIG. 9 is a flowchart illustrating a method ofoperating the CMOS image sensor according to another embodiment of theinvention. Also, referring to FIG. 7 along with the aforesaid CMOS imagesensor 3, the method of operating the CMOS image sensor of the inventioncomprises the following steps once the sensing region 304 exceeds a realregion of the pixel array unit 30.

In the beginning, step S200 is performed to sense an object or a movingtrajectory thereof by the pixel array unit 30. Afterward, step S202 isperformed to determine the sensing region 304 corresponding to theobject or the moving trajectory thereof. Step S204 is then performed togenerate a row selection signal. Step S206 is then performed to controlthe multiplexers, which are electrically connected to the pixels P2, P6,P1, P5 and P9 within the sensing region 304, to transmit the rowselection signal to the pixels P2, P6, P1, P5 and P9. Step S208 is thenperformed to judge whether the sensing region 304 exceeds a real regionof the pixel array unit 30, and step S210 is then performed if it isYES, otherwise, step S212 is performed. Step 210 is performed to add thedummy pixel P0 to the sensing region 304. Step S212 is performed to readsignals generated by the dummy pixel P0, if any, and the pixels P2, P6,P1, P5 and P9 of the sensing region 304 in row-major order.

Referring to FIG. 10, FIG. 10 is a schematic diagram illustrating acircuit of a CMOS image sensor 3′ according to another embodiment of theinvention. As shown in FIG. 10, the CMOS image sensor 3′ comprises apixel array unit 30′, a row selection unit 32, a logic circuit 34 and aread-out circuit 36 wherein the principles of the row selection unit 32,the logic circuit 34 and the read-out circuit 36 are the same as thosementioned in the above and will not be described in detail here. In thisembodiment, the pixel array unit 30′ has a 4*5 pixel array. In otherwords, the pixel array unit 30′ comprises twenty pixels P1-P20. Comparedto the pixel array unit 30 shown in FIG. 6, an amount of themultiplexers of the pixel array unit 30′ is less than that of thepixels. As shown in FIG. 10, the pixel array unit 30′ comprisesseventeen multiplexers wherein the pixels P1 and P2 are electricallyconnected to one single multiplexer 302 a, the pixels P3 and P4 areelectrically connected to one single multiplexer 302 b, and the pixelsP11 and P12 are electrically connected to one single multiplexer 302 c.That is to say, the invention may utilize one multiplexer to controlmore than one pixel simultaneously so as to reduce the amount ofmultiplexers. The amount of pixels, which are electrically to one singlemultiplexer, can be determined based on practical applications and isnot limited to two as shown in FIG. 10. It should be noted that if thereare at least two pixels electrically connected to one singlemultiplexer, the at least two pixels are located at different columns ofthe pixel array unit 30′. As shown in FIG. 10, the pixels P1 and P2 arelocated at different columns, the pixels P3 and P4 are located atdifferent columns, and the pixels P11 and P12 are located at differentcolumns. Preferably, the pixels, which are electrically connected to onesingle multiplexer, may be, but not limited to, located at one row ofthe pixel array unit 30′. As shown in FIG. 10, the pixels P1 and P2 arelocated at one row, the pixels P3 and P4 are located at one row, and thepixels P11 and P12 are located at one row.

Referring to FIGS. 11 and 12, FIG. 11 is a schematic diagramillustrating a CMOS image sensor 5 according to another embodiment ofthe invention, and FIG. 12 is a time sequence diagram illustratingreading order of pixel data. As shown in FIG. 11, the CMOS image sensor5 comprises a pixel array unit 50, a column selection unit 52, a logiccircuit 54, a read-out circuit 56 and a frame buffer 58. The columnselection unit 52, the logic circuit 54 and the read-out circuit 56 areelectrically connected to the pixel array unit 50, and the frame buffer58 is electrically connected to the read-out circuit 56. The 4*3 pixelarray shown in FIG. 11 is used for illustrative purpose only and theinvention is not limited to that manner. The pixels P1-P12 can absorblight reflected from an object and then transform the absorbed lightinto an electric signal. The pixels P1-P12 usually consist oftransistors and photo diodes. It should be noted that the structure andprinciple of the pixels P1-P12 can be easily achieved by one skilled inthe art and thus will not be described in detail here.

The column selection unit 52 receives a time sequence signal and acontrol signal from a controller (not shown) and generates a columnselection signal. The column selection signal is used for controllingthe pixels P1-P12 of the pixel array unit 50 to output data. The logiccircuit 54 is used for determining a sensing region corresponding to anobject or a moving trajectory thereof sensed by the pixel array unit 50.The read-out circuit 56 reads signals generated by the pixels of thesensing region in column-major order. Afterward, the frame buffertransforms the output data from column-major order to row-major order.

For example, when a user uses an object (not shown), such as finger,stylus or the like, to operate an optical positioning system (not shown)equipped with the CMOS image sensor 5, the pixel array unit 50 willsense the object or a moving trajectory thereof. Afterward, the logiccircuit 54 determines a sensing region 504 corresponding to the objector the moving trajectory thereof sensed by the pixel array unit 50. Asshown in FIG. 11, the sensing region 504 comprises five pixels P2, P3,P7, P8 and P12. It should be noted that because the sensing region 504shown in FIG. 11 exceeds a real region of the pixel array unit 50, thescanning time may become unstable every time and thus the calculation ofexposure time may increase. To solve this problem, the read-out circuit56 of the invention can add a dummy pixel P0 to the sensing region 504while reading pixel data so as to keep the scanning time in constantevery time and simplify the calculation of exposure time.

Based on the column selection signal generated by the column selectionunit 52, the read-out circuit 56 reads signals generated by the pixelsof the sensing region 504 in column-major order wherein the readingorder is as follows, P0, P2, P3, P7, P8 and P12. Afterward, the framebuffer 58 transforms the output data form column-major order torow-major order. As shown in FIG. 12, after being transformed by theframe buffer 58, the reading order is changed to be as follows, P0, P3,P8, P2, P7 and P12. Furthermore, in this embodiment, since the scanningline is not orthogonal to the contour of the object, the scanning resultmay show an oblique contour. The invention utilizes the frame buffer 58to rearrange the pixel data so as to improve the aforesaid problem.

Referring to FIG. 13, FIG. 13 is a schematic diagram illustrating a CMOSimage sensor 7 according to another embodiment of the invention. Asshown in FIG. 13, the CMOS image sensor 7 comprises a pixel array unit70, a row selection unit 72, a logic circuit 74 and a read-out circuit76. The row selection unit 72 and the read-out circuit 76 areelectrically connected to the pixel array unit 70. The logic circuit 74is electrically connected to the read-out circuit 76.

The pixel array unit 70 is used for sensing an object (not shown) or amoving trajectory thereof. In this embodiment, the pixel array unit 70comprises M pixels 700 wherein M is a positive integer. In addition, thepixel 700 can absorb light reflected from an object and then transformthe absorbed light into an electric signal. The pixel 700 usuallyconsists of transistors and photo diodes. It should be noted that thestructure and principle of the pixel 700 can be easily achieved by oneskilled in the art and thus will not be described in detail here.

The row selection unit 72 receives a time sequence signal and a controlsignal from a controller (not shown) and then generates a row selectionsignal. The row selection signal is used for controlling the pixels 700of the pixel array unit 70 to output data. The read-out circuit 76 readssignals generated by the pixels 700 of the pixel array unit 70. Thelogic circuit 74 is used for determining a sensing region correspondingto the object or the moving trajectory thereof wherein the sensingregion comprises N of the M pixels 700 and N is a positive integersmaller than or equal to M. Afterward, the logic circuit 74 determines afirst pixel and a last pixel for each row within the sensing region andcontrols the read-out circuit 76 to read the first pixel through thelast pixel of each row in row-major order, so as to output signalsgenerated by the N pixels.

Referring to FIGS. 14 and 15, FIG. 14 is a schematic diagramillustrating the pixel array unit 70 shown in FIG. 13 having a 3*3 pixelarray, and FIG. 15 is a schematic diagram illustrating a circuit of theCMOS image sensor 7 shown in FIG. 14. The 3*3 pixel array shown in FIGS.14 and 15 is used, for example, to depict features of the invention.

When a user uses an object (not shown), such as finger, stylus or thelike, to operate an optical positioning system (not shown) equipped withthe CMOS image sensor 7, the pixel array unit 70 will sense the objector a moving trajectory thereof. Afterward, the logic circuit 74determining a sensing region 704 according to the object or the movingtrajectory thereof sensed by the pixel array unit 70. As shown in FIG.14, the sensing region 704 comprises five pixels P1, P2, P5, P6 and P9.That is to say, the aforesaid N is equal to 5. Furthermore, the pixelsP1 and P2 are located at the first row, the pixels P5 and P6 are locatedat the second row, and the pixel P9 is located at the third row. Then,the logic circuit 74 determines a first pixel and a last pixel for eachrow within the sensing region 704. As shown in FIG. 14, for the firstrow within the sensing region 704, the first pixel is P1 and the lastpixel is P2; for the second row within the sensing region 704, the firstpixel is P5 and the last pixel is P6; and for the third row within thesensing region 704, the first pixel is P9 and the last pixel is also P9.Then, the logic circuit 74 controls the read-out circuit 76 to read thefirst pixel through the last pixel of each row in row-major order, so asto output signals generated by the five pixels within the sensing region704. In this embodiment, the red-out circuit 76 will read the pixels P1,P2, P5, P6 and P9 within the sensing region 704 in order.

In this embodiment, the sensing region 704 is variable and can be setthrough self-calibration while booting. Furthermore, when the object orthe moving trajectory thereof has a random shape, the logic circuit 74may determine the sensing region as a parallelogram including the objector the moving trajectory thereof so as to prevent the followingalgorithm from getting complicated.

It should be noted that because the sensing region 704 shown in FIG. 14exceeds a real region of the pixel array unit 70, the scanning time maybecome unstable every time and thus the calculation of exposure time mayincrease. To solve this problem, the read-out circuit 76 of theinvention can add dummy pixel(s) to the sensing region 704 while readingpixel data so as to keep the scanning time inconstant every time andsimplify the calculation of exposure time. Referring to FIG. 16, FIG. 16is a schematic diagram illustrating the sensing region 704 shown in FIG.14 with a dummy pixel P10. As shown in FIG. 16, after adding the dummypixel P10, the pixels within the sensing region 704 are arranged as aparallelogram and an amount of pixels in each row is the same.Accordingly, the scanning time can be kept in constant every time. Atthis time, for the third row within the sensing region 704, the firstpixel is P9 and the last pixel is the dummy pixel P10.

Referring to FIG. 17, FIG. 17 is a schematic diagram illustrating asensing region 704′ according to another embodiment of the invention.Besides the aforesaid parallelogram, the read-out circuit 76 of theinvention may also read and output pixel data within the sensing region704′ shown in FIG. 17 through appropriate setting. It should be notedthat since the second row within the sensing region 704′ includes sixpixels P10, P11, P12, P14, P15 and P16 and there is a break between thepixels P10, P11, P12 and the other pixels P14, P15, P16, the logiccircuit 74 will determine a first pixel and a last pixel for the pixelsP10, P11, P12 and determine another first pixel and another last pixelfor the pixels P14, P15, P16. In other words, for the pixels P10, P11,P12, the first pixel is P10 and the last pixel is P12; and for thepixels P14, P15, P16, the first pixel is P14 and the last pixel is P16.Therefore, for the second row shown in FIG. 17, the read-out circuit 76will read the first pixel P10 through the last pixel P12 first and thenread another first pixel P14 through another last pixel P16. That is tosay, the pixels within each row read by the read-out circuit 76 can becontinuous or non-continuous, and it depends on the sensing region.

Referring to FIG. 18, FIG. 18 is a flowchart illustrating a method ofoperating the CMOS image sensor according to another embodiment of theinvention. Also, referring to FIGS. 13 to 15 along with the aforesaidCMOS image sensor 7, the method of operating the CMOS image sensor ofthe invention comprises the following steps.

In the beginning, step S300 is performed to sense an object or a movingtrajectory thereof by the pixel array unit 70. Afterward, step S302 isperformed to determine the sensing region 704 corresponding to theobject or the moving trajectory thereof. Step S304 is then performed togenerate a row selection signal for controlling the pixels of the pixelarray unit 70 to output signals. Step S306 is then performed todetermine a first pixel and a last pixel for each row within the sensingregion 704. Step S308 is then performed to read the first pixel throughthe last pixel of each row in row-major order. Finally, step S310 isperformed to output signals generated by the pixels P1, P2, P5, P6 andP9 of the sensing region 704.

Referring to FIG. 19, FIG. 19 is a flowchart illustrating a method ofoperating the CMOS image sensor according to another embodiment of theinvention. Also, referring to FIG. 16 along with the aforesaid CMOSimage sensor 7, the method of operating the CMOS image sensor of theinvention comprises the following steps once the sensing region 704exceeds a real region of the pixel array unit 70.

In the beginning, step S400 is performed to sense an object or a movingtrajectory thereof by the pixel array unit 70. Afterward, step S402 isthen performed to determine the sensing region 704 corresponding to theobject or the moving trajectory thereof. Step S404 is then performed togenerate a row selection signal for controlling the pixels of the pixelarray unit 70 to output signals. Step S406 is then performed to judgewhether the sensing region 704 exceeds a real region of the pixel arrayunit 70, and step S408 is then performed if it is YES, otherwise, stepS410 is performed. Step 408 is performed to add the dummy pixel P10 tothe sensing region 704. Step S410 is performed to determine a firstpixel and a last pixel for each row within the sensing region 704. StepS412 is then performed to read the first pixel through the last pixel ofeach row in row-major order. Finally, step S414 is performed to outputsignals generated by the pixels P1, P2, P5, P6, P9 and the dummy pixelP0, if any, of the sensing region 704.

Compared to the prior art, the invention utilizes multiplexers tocontrol output of pixel data. The logic circuit can control themultiplexers to define a slope of scanning line selected by each rowselection signal. Furthermore, the invention can read the pixel data ofthe sensing region in column-major order first and then transform theoutput data from column-major order to row-major order by using theframe buffer. Moreover, the invention may add a logic circuit to theread-out circuit and utilize the logic circuit to determine a startingpoint (i.e. the aforesaid first pixel) and a terminal point (i.e. theaforesaid last pixel) for each row within the sensing regioncorresponding to the sensed object or the moving trajectory thereof, soas to control the read-out circuit to output the pixel data within thesensing region. Since the invention only needs to output pixel datawithin the sensing region corresponding to the object or the movingtrajectory thereof, the operating frequency and power consumption can bereduced substantially. Moreover, once the logic circuit judges that thesensing region exceeds the real region of the pixel array unit, theread-out circuit can add dummy pixel(s) to the sensing region so as tokeep the scanning time in constant every time and simplify thecalculation of exposure time.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention.

1. A CMOS image sensor comprising: a pixel array unit for sensing anobject, the pixel array unit comprising M pixels and P multiplexers,each of the M pixels being electrically connected to one of the Pmultiplexers wherein M is a positive integer and P is a positive integersmaller than or equal to M; a row selection unit, electrically connectedto the P multiplexers, for generating a row selection signal; and alogic circuit, electrically connected to the P multiplexers, fordetermining a sensing region corresponding to the object wherein thesensing region comprises N of the M pixels and N is a positive integersmaller than or equal to M, the logic circuit controlling Qmultiplexers, which are electrically connected to the N pixels, totransmit the row selection signal to the N pixels wherein Q is apositive integer smaller than or equal to N and smaller than or equal toP.
 2. The CMOS image sensor of claim 1, further comprising a read-outcircuit, electrically connected to the pixel array unit, for readingsignals generated by the N pixels of the sensing region.
 3. The CMOSimage sensor of claim 2, wherein the read-out circuit reads the signalsgenerated by the N pixels of the sensing region in row-major order. 4.The CMOS image sensor of claim 2, wherein when the sensing regionexceeds a real region of the pixel array unit, the read-out circuit addsat least one dummy pixel to the sensing region.
 5. The CMOS image sensorof claim 1, wherein the sensing region is a parallelogram.
 6. The CMOSimage sensor of claim 1, wherein when P is smaller than M, at least twoof the M pixels are electrically connected to one of the P multiplexerssimultaneously and the at least two pixels are located at differentcolumns of the pixel array unit.
 7. The CMOS image sensor of claim 6,wherein the at least two pixels are located at one row of the pixelarray unit.
 8. A method of operating a CMOS image sensor comprisingsteps of: sensing an object by a pixel array unit, the pixel array unitcomprising M pixels and P multiplexers, each of the M pixels beingelectrically connected to one of the P multiplexers wherein M is apositive integer and P is a positive integer smaller than or equal to M;determining a sensing region corresponding to the object wherein thesensing region comprises N of the M pixels and N is a positive integersmaller than or equal to M; generating a row selection signal; andcontrolling Q multiplexers, which are electrically connected to the Npixels, to transmit the row selection signal to the N pixels wherein Qis a positive integer smaller than or equal to N and smaller than orequal to P.
 9. The method of claim 8, further comprising step of readingsignals generated by the N pixels of the sensing region in row-majororder.
 10. The method of claim 8, further comprising step of adding atleast one dummy pixel to the sensing region when the sensing regionexceeds a real region of the pixel array unit.
 11. The method of claim8, wherein the sensing region is a parallelogram.
 12. The method ofclaim 8, wherein when P is smaller than M, at least two of the M pixelsare electrically connected to one of the P multiplexers simultaneouslyand the at least two pixels are located at different columns of thepixel array unit.
 13. The method of claim 12, wherein the at least twopixels are located at one row of the pixel array unit.
 14. A CMOS imagesensor comprising: a pixel array unit for sensing an object, the pixelarray unit comprising M pixels, wherein M is a positive integer; a rowselection unit, electrically connected to the pixel array unit, forgenerating a row selection signal, the row selection signal controllingthe M pixels to output signals; a read-out circuit, electricallyconnected to the pixel array unit, for reading signals generated by theM pixels; and a logic circuit, electrically connected to the read-outcircuit, for determining a sensing region corresponding to the objectwherein the sensing region comprises N of the M pixels and N is apositive integer smaller than or equal to M, the logic circuitdetermining a first pixel and a last pixel for each row within thesensing region and controlling the read-out circuit to read the firstpixel through the last pixel of each row in row-major order, so as tooutput signals generated by the N pixels.
 15. The CMOS image sensor ofclaim 14, wherein when the sensing region exceeds a real region of thepixel array unit, the read-out circuit adds at least one dummy pixel tothe sensing region.
 16. The CMOS image sensor of claim 14, wherein thesensing region is a parallelogram.
 17. A method of operating a CMOSimage sensor comprising steps of: sensing an object by a pixel arrayunit, the pixel array unit comprising M pixels wherein M is a positiveinteger; determining a sensing region corresponding to the objectwherein the sensing region comprises N of the M pixels and N is apositive integer smaller than or equal to M; generating a row selectionsignal for controlling the M pixels to output signals; determining afirst pixel and a last pixel for each row within the sensing region;reading the first pixel through the last pixel of each row in row-majororder; and outputting signals generated by the N pixels.
 18. The methodof claim 17, further comprising step of adding at least one dummy pixelto the sensing region when the sensing region exceeds a real region ofthe pixel array unit.
 19. The method of claim 17, wherein the sensingregion is a parallelogram.